with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a few peaks
with a duration of about 25 sec. The peak count rate
was ~2600 counts/sec (15-350 keV), at ~6 sec after the trigger.
The XRT began observing the field at 03:07:36.2 UT, 66.2 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 57.1719,
65.9012 which is equivalent to:

RA(J2000) = 03h 48m 41.25s
Dec(J2000) = +65d 54' 04.4"

with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 117 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (4.54 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 5.9
(+4.29/-3.55) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 250 seconds with the U filter starting
281 seconds after the BAT trigger. No credible afterglow candidate has been
found in the initial data products. The 2.7'x2.7' sub-image covers none of the
XRT error circle. The 8'x8' region for the list of sources generated on-board
covers 100% of the XRT error circle. The list of sources is typically complete
to about 18.0 mag. No correction has been made for the expected extinction
corresponding to E(B-V) of 1.10.
Burst Advocate for this burst is A. Amaral-Rogers (aar14 AT le.ac.uk).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

GCN Circular #18612
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), A. Sota (IAA-CSIC),
and C. Thoene (IAA-CSIC) report:
We observed the field of GRB 151118A (Amaral-Rogers et al. GCN 18611)
with the 1.5 m OSN telescope in Granada (Spain), starting at 03:17:55 UT
(11.42 min after the GRB onset). Observations consisted of 7x300 s
exposures in I-band. No new source is detected within the XRT error box.
The 3-sigma limiting magnitudes of the individual exposures, and the combined
frames are I(Vega) = 21.5 mag, and I(Vega) = 22.5 mag, respectively. The mean
time of the combined exposure is 03:37:49 (31.32 min after the burst). Photometry
was obtained by comparison with stars from the USNO-B1.0 catalogue.

GCN Circular #18613
V. Lipunov, E.Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa,
A.Kuznetsov, D. Vlasenko, D.Kuvshinov
Lomonosov Moscow State University, Sternberg Astronomical Institute
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik
Kislovodsk Solar Station of the Pulkovo Observatory
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in Kislovodsk was pointed to the GRB151118.13 30 sec after notice
time and 44 sec after trigger time at 2015-11-18 03:07:17 UT. On our first
(10s exposure) set we haven`t found optical transient within SWIFT
error-box (ra=03 48 37 dec=+65 52 06 r=0.05).
The 5-sigma upper limit has been about 16.5 mag unfiltered.
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in IAC was pointed to the GRB151118A 24 sec after notice time
and 42 sec after trigger time at 2015-11-18 03:07:12 UT in two
polarizations. On our first (10s exposure) set we haven`t found optical
transient within SWIFT error-box (Amaral-Rogers et al GCN 18611).
Our early upper limits on single and coadd images given in a table below:
Table 1.
5 sigma limit.

with an uncertainty of 1.6 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.

If the light curve continues to decay with a power-law decay index of
1.07, the count rate at T+24 hours will be 4.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.4 x
10^-13 (4.2 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00664078.
This circular is an official product of the Swift-XRT team.

with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 98%.
The mask-weighted light curve shows a multi-peaked structure that
starts at ~ T0 and ends at ~T+30 s. The structure contains roughly two main
pulses that peak at ~ T0 and ~T+7 s, respectively. T90 (15-350 keV) is
23.4 +- 10.5 sec (estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+30.8 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.80 +- 0.20. The fluence in the 15-150 keV band is 4.5 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+6.41 sec in the 15-150 keV band
is 1.2 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/664078/BA/

GCN Circular #18642
Y. Kitaoka, T. Sakamoto, A. Yoshida (AGU)
We observed the field of GRB 151118A detected by Swift (trigger #664078;
Amaral-Rogers et al., GCN Circ. 18611) with the iTelescope.Net (http://www.itelescope.net)
T7 (17" Plane Wave) telescope located at the AstroCamp Observatory (Nerpio, Spain).
20 images of 60 sec exposures were taken in the R filter starting from November 18 03:45:22 (UT)
about 38.8 minutes after the trigger and stopped on November 18 04:23:04 (UT).
We do not detect the optical afterglow both in the individual images and the stacked image
at the enhanced X-ray afterglow position (Evans et al., GCN Circ. 18614). The estimated
five sigma upper limit of the combined image (total exposure of 1200 sec) is ~18.3 using
the USNO-B1 catalog.